Specialty Cement, Concrete, and Mortar Information
Specialty cement, concrete and mortar contain specialized binders such as K silicate, calcium aluminate, sulfur, and oxysulfate or polymer resins. They cure or set through film drying (air setting), chemical reactions, thermoset bonds, hydraulic bonds, hot melting, and multiple component binder systems. Unlike conventional construction products, specialty concrete is not based on Portland cement. Instead, specialty concrete consists of specialty cement such as potassium silicate that is mixed with water, a coarse aggregate such as gravel or crushed stone, and a fine aggregate or sand. Specialty mortar is a mixture of a specialty binder or clinker and a fine aggregate. Specialty cement, concrete and mortar are used to join components and form structures. Products such as grout and caulk are used to fill gaps between tiles and bricks. Thin set materials such as dry set mortar and dry bond mortar include cement and are used in coating products. Cement-based liners or lining systems are much heavier or are applied in thicker layers than thin set materials. Pre-cast shapes such as blocks and sheets are commonly available.
There are several chemical systems for specialty cement, concrete, and mortar.
Bond or binder types include calcium aluminate, phosphate, potassium silicate, slag cement, sulfur cement, and sulfate or gypsum. Polymer modified bonds are also available. For example, acrylic binders provide excellent environmental resistance and fast setting times. Epoxy resins or binders exhibit high strength and low shrinkage during cure. They also offer toughness and resistance to chemical and environmental damage. Furan resins are formed from the polymerization or poly condensation of furfural, furfural alcohol, or other compounds containing a furan ring. They are commonly used in foundry binders, grinding wheels, refractories and other high-temperature applications. Polyurea resins or binders are used in place of phenolics or other formaldehyde resins in particle or fiberboard binder applications. Polyurethane provides excellent flexibility, impact resistance and durability. Other chemical systems for specialty cement, concrete and mortar include silicone, polyester, and vinyl ester.
Recommended mixing, dispensing and curing of ceramic-based adhesives. Video credit: JohnDavisSAU / CC BY-SA 4.0
Variations in Specialty Cement, Concrete and Mortar
Specialty cement, concrete and mortar vary in terms of basic specifications and mechanical, electrical and thermal properties.
Basic specifications include set/cure time, set/cure temperature, density, and shrinkage.
- Density is measured as the mass per unit area.
- Shrinkage is expressed as a maximum percentage.
Mechanical properties for specialty cement, concrete and mortar include compressive strength, bond strength, tensile strength, and modulus of rupture (MOR).
Electrical properties include electrical resistivity, dielectric strength and relative permittivity. The dielectric constant is the relative permittivity of a material compared to a vacuum or free space.
Thermal properties for specialty concrete and mortar include service temperature, thermal conductivity, and the coefficient of thermal expansion (CTE), the amount of linear expansion or shrinkage that occurs in a material with a change in temperature.
Features and Applications
There are a variety of features and applications for specialty cement, concrete, and mortar. Some products are abrasion resistant, castable, chemical resistant, conductive, fiber-reinforced, sprayable, or waterproof. Other products provide protection against wear, corrosion, or electrostatic discharge (ESD). Specialty cement, concrete and mortar are often used in electrical power and high voltage (HV) applications. Some products are used as fillers and sealants. Dry and wet gunning mixes (e.g., shotcrete or gunnite) load with gun-like devices to form walls. Wet ram cements have enough plasticity to allow a wet mix to be rammed or formed into place. Mortars, patching compounds and finishing cements with good troweling or trowel-on properties are also available.
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